The present invention is directed to electrical power connections, and especially to electrical power connections for use in equipment cabinets where a low profile is desirable for such connections in order to conserve space.
Power cabinet installations typically contain shelves of battery strings that maintain the output voltage for equipment or to equipment during AC utility outages. The battery strings require routine maintenance during which the strings must be disconnected from the plant output voltage so that an accidental short during the maintenance procedure does not shut the plant down. Typically this disconnection is accomplished using commercially available battery disconnect switches. However, at high current levels (e.g., 200 Amp and above) the commercially available battery disconnect switches are unacceptable large and expensive. As power density requirements for DC battery plants increase, the size of the required disconnect devices becomes prohibitive.
The trend in today""s electrical products is largely toward smaller products. For example, telecommunication switches are becoming smaller as they are installed in population-dense areas rather than in wide-open fields. Other electrical and communication products are similarly tending toward smaller product configurations.
There is a need for a compact, quick disconnect switch having capacity for handling high currents for use in disconnecting power from equipment, including plant power supply equipment. There is a special need for a compact high current quick disconnect switch for disconnecting back-up batteries from equipment and from house-supplied power circuits.
An apparatus for effecting electrical connection between a power source and equipment includes: (a) a first conductor having a first aperture; (b) a second conductor having a second aperture; (c) an insulator having a connecting bore coaxial with the first and second apertures to establish a bridging passage extending a bridging distance to traverse the first conductor, the insulator and the second conductor when assembled with the first conductor and the second conductor substantially parallel separated by the insulator; and (d) a bridge having an axial length at least equal with the bridging distance and a transaxial dimension less than the passage diameter and having a first engagement structure in the first aperture and a second engagement structure in the second aperture when the bridge is engaged; the bridge is removable from engagement to interrupt electrical connection between the power source and the equipment.
Because of the significant weight of the battery strings in many equipment cabinets (typically above 100 pounds per shelf), many battery shelves contain reinforcing flanges oriented substantially perpendicular with the plane of the shelf. Such reinforcing flanges help to stiffen and strengthen the shelf structure. Some stiffening flanges are located at the front of the shelf running across the shelf width. The preferred embodiment of the apparatus of the present invention fits within the profile of such a stiffening flange for a battery shelf. By such a configuration, no significant extra space is required for accommodating disconnect switches configured according to the present invention.
The invention is preferably embodied in a low profile, low cost, high current battery disconnect switching apparatus that employs a pin and socket type of interconnect between power supply (e.g., batteries) and equipment. The apparatus can handle extremely high battery currents (e.g., up to 400 Amps). Moreover, the apparatus is configured to easily accommodate parallel or serial connection between power supply (e.g., batteries) and equipment, thereby permitting flexibility in designing current handling capacity for particular embodiments of the apparatus. The apparatus preferably is comprised of two elements. A receptacle element includes, by way of example and not by way of limitation, two sets of conductive members or bus bars separated by an insulator. The insulator provides the requisite separation of the bus bars to preclude shorting or arcing and provides flanges for mounting the apparatus in a cabinet, for example to a battery shelf. In the exemplary embodiment, one set of bus bars is connected to the either the positive or negative side of the battery string via a cable lug mounted to a stud in the bus bar. The other set of bus bars is connected directly to the plant voltage via either cable or bus bar. The apparatus is preferably mounted into the front edge of the battery shelf and takes up a frontal area of approximately 0.75xe2x80x3xc3x978.5xe2x80x3. Alternatively, the apparatus may be mounted in a vertical strength member or other structural member and occupy a similar frontal area.
The second element of the apparatus is a pin assembly configured for insertion into aligned apertures in the two sets of bus bars and the insulator. The pin assembly passes the battery current from one set of bus bars (e.g., the battery-connected bus bars) to the other set of bus bars (e.g., the plant output-connected bus bars). The pin assembly preferably includes a brass shaft with channels machined-in to retainingly receive two flexible conducting engaging collars for providing reliable electrical contact with each of the sets of bus bars. The pin assembly is preferably equipped with a handle to facilitate easy insertion and removal as well as to provide a positive stop for the pin to prevent over-insertion or under-insertion. When the pin assembly is removed from the apparatus the electrical connection between the two sets of bus bars is broken, thereby disconnecting the plant output from the battery terminals. In such manner, the battery string is easily disconnected and ready for maintenance. Any arcing which may occur during the disconnection process is contained within the insulator, thereby protecting both the user and the equipment from damage.
The disconnect apparatus is preferably modular in construction. Each pin can handle, for example, up to 200 Amps of battery current, so for applications up to 200 Amps only one disconnecting pin is required. For higher current applications a second pin may be added in parallel with the first pin to increase the current-carrying capacity of the apparatus. In such configurations, it is preferred that pin assemblies be ganged together to ensure that the multiple pin assemblies are inserted and removed substantially simultaneously in order to avoid having one of the pin assemblies carrying greater than its capacity of current even for a short period. Such a modular construction design provides a cost-effective solution that accommodates current capacity growth along with plant growth as systems expand.
It is therefore an object of the present invention to provide an apparatus and method for effecting electrical connection between a power source and equipment that is preferably embodied in a compact, quick disconnect switch having capacity for handling high currents.
It is a further object of the present invention to provide an apparatus and method for effecting electrical connection between a power source and equipment that is configured for employment as a compact high current quick disconnect switch for disconnecting back-up batteries from equipment and from house-supplied power circuits.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.